65 research outputs found
SALT observations of southern post-novae
We report on recent optical observations of the stellar and the nebular
remnants of 22 southern post-novae. In this study, for each of our targets, we
obtained and analysed long-slit spectra in the spectral range 3500-6600 A and
in H+NII narrow-band images. The changes in the emission lines'
equivalent widths with the time since the outburst agree with earlier published
results of other authors. We estimated an average value =2.37 for the
exponent of the power law fitted to the post-novae continua. Our observations
clearly show the two-component structure of the V842 Cen expanding nebulae,
owing to the different velocities of the ejected matter. We discovered an
expanding shell around V382 Vel with an outer diameter of about 12 arcsec.Comment: 24 pages, 19 figures, A&A accepte
Discovery of a Magnetic White Dwarf in the Symbiotic Binary Z Andromedae
We report the first result from our survey of rapid variability in symbiotic
binaries: the discovery of a persistent oscillation at P=1682.6 +- 0.6 s in the
optical emission from the prototype symbiotic, Z Andromedae. The oscillation
was detected on all 8 occasions on which the source was observed over a
timespan of nearly a year, making it the first such persistent periodic pulse
found in a symbiotic binary. The amplitude was typically 2 - 5 mmag, and it was
correlated with the optical brightness during a relatively small outburst of
the system. The most natural explanation is that the oscillation arises from
the rotation of an accreting, magnetic (B_S > 10^5 G) white dwarf. This
discovery constrains the outburst mechanisms, since the oscillation emission
region near the surface of the white dwarf was visible during the outburst.Comment: Accepted for publication in the Astrophysical Journal (6 pages,
including 4 figures), LaTe
Tomographic Simulations of Accretion Disks in Cataclysmic Variables - Flickering and Wind
Both continuum and emission line flickering are phenomena directly associated
with the mass accretion process. In this work we simulate accretion disk
Doppler maps including the effects of winds and flickering flares. Synthetic
flickering Doppler maps are calculated and the effect of the flickering
parameters on the maps is explored. Jets and winds occur in many astrophysical
objects where accretion disks are present. Jets are generally absent among the
cataclysmic variables (CVs), but there is evidence of mass loss by wind in many
objects. CVs are ideal objects to study accretion disks and consequently to
study the wind associated with these disks. We also present simulations of
accretion disks including the presence of a wind with orbital phase resolution.
Synthetic H-alpha line profiles in the optical region are obtained and their
corresponding Doppler maps are calculated. The effect of the wind simulation
parameters on the wind line profiles is also explored. From this study we
verified that optically thick lines and/or emission by diffuse material into
the primary Roche lobe are necessary to generate single peaked line profiles,
often seen in CVs. The future accounting of these effects is suggested for
interpreting Doppler tomography reconstructions.Comment: 9 pages, 9 figure
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